PREFACE. IX 



was published in English. In the Introduction, the 

 author writes as if it were a perfectly well understood 

 thing that species have arisen by adaptations to the 

 iufluences of the environment.* 



In 1886, Mr. Herbert Spencer contributed two articles 

 on " The Factors of Organic Evolution " to the Nineteenth 

 Ceniv/ry.^ In these he showed, from many passages in 

 Mr. Darwin's works, especially "Animals and Plants 

 under Domestication " and in his later volumes, that he 

 became much more favourably inclined to the belief that 

 the effects of the environment were accumulative, and 

 that in the course of some generations the variations set 

 up tended to cease and become fixed. Mr. Spencer par- 

 ticularly notes the change of view, as illustrated by the 

 expression " little doubt " being replaced by " no doubt " 

 in the following sentence: "I think there can be no 

 doubt that use in our domestic animals has strengthened 

 and enlarged certain parts, and disuse diminished them ; 

 and that such modifications are inherited." J It may 

 be added that in " The Cross and Self Fertilisation of 

 Flowers" (1876), and in "Forms of Flowers" (1877), 

 Mr. Darwin makes many observations upon the effects 

 of the external conditions upon plants as influencing and 

 modifying them in various ways. It is curious to note 

 that the three influences upon which Lfimarck laid 



* See, e.g., p. 25. t See p. 570 and p. 749. 



X "tJse" and "disuse" in animals corresponds to what I have 

 called " hypertrophy " and " atrophy " in plants, in this work. 



